(1) Field of the Invention
The present invention relates to a semiconductor wafer holding method and a semiconductor wafer holding structure each used for holding a semiconductor wafer in preprocessing in which the semiconductor wafer is transported or a workpiece is subjected to various processes. In particular, the present invention relates to a technique for holding a semiconductor wafer in such a manner that the semiconductor wafer is joined to a ring frame through a supporting adhesive tape.
(2) Description of the Related Art
For example, JP-A 2003-234392 discloses a technique for obtaining a semiconductor chip from a semiconductor wafer (hereinafter, simply referred to as a “wafer”). According to this technique, a wafer is joined to a supporting adhesive tape joined to a ring frame such that the ring frame holds the wafer; thus, a semiconductor wafer holding structure is prepared. Then, the semiconductor wafer holding structure is subjected to a dicing process, so that the wafer held and supported by the ring frame is divided into a plurality of semiconductor chips.
In recent years, however, a wafer has been made thinner in response to needs for size reduction and high-density package as to an electronic device. In order to fill the needs, the recent wafer has a thickness of several tens of micrometers. Such a wafer having a considerably small thickness is susceptible to damage such as cracking or chipping due to bending or warping and, therefore, requires careful handling. For ease of the handling, a center of a back face of the wafer is ground to form an annular convex portion at an outer periphery of the back face. Thus, the wafer is allowed to have rigidity during a period from grinding of the back face to holding of the wafer by a ring frame.
The formation of the annular convex portion is effective in handling of the wafer until the wafer is held by the ring frame. If the back face of wafer is held by the ring frame through an adhesive tape prior to performance of a dicing process, the annular convex portion comes into close contact with the adhesive tape, but a flat concave portion corresponding to the ground center does not come into close contact with the adhesive tape. Consequently, there is a problem that the flat concave portion becomes susceptible to damage when the wafer is divided into chips in the dicing process.